Locking mechanisms for door assemblies have long been used on a wide variety of doors to a chamber and/or room that is desired to be isolated. Examples of various types of locking structures are shown in U.S. Pat. Nos. 1,269,572; 2,664,611; 4,114,933; and 4,342,207.
However, if the chamber and/or room that is to be secured requires an ability to maintain an greater pressure from within the chamber than exists outside the chamber, additional pressure-related considerations must be taken into account. Such pressure vessel closure assemblies have long been known and include a wide variety of structures as shown in U.S. Pat. Nos. 2,010,200 and 3,258,151. Of the types of pressure closure assemblies for pressure vessels utilizing some type of annular or radially expanding element, some examples are shown in U.S. Pat. Nos. 2,196,895; 4,102,474; 4,315,577; and 4,489,850. However, so far as known, all of the aforementioned pressure vessel closure members require a locking structure mechanism that is in part contained within the door assembly itself. In some cases, as for example with U.S. Pat. No. 4,102,474, a central portion of a closure member is required to be maintained at a pressure in order to properly actuate particular elements thereof in order to accomplish the locking operation. In like fashion, U.S. Pat. No. 4,315,577 discloses a centrally mounted operator rotating in such a fashion that the locking elements are individually and independently moved outwardly based upon movement of a pin in a spiraling track. Likewise, in U.S. Pat. No. 4,489,850, the door mechanism contains a plurality of locking pawls contained with the door assembly which move radially outwardly into an engaging position with the pressure vessel to effectuate sealable engagement therewith, with the locking pawls having elongate slots formed therein.
Thus, so far as known, no pressure vessel closure member is available for securement of the pressure vessel door by the radial contraction of the retaining elements about a pressure vessel door which has no sealably movable parts therewith.